I would like to be notified when my garage door has been left open for greater than x minutes. Has anyone done this?
Here is a simple webCore piston. This one only runs when the SHM is armed (I haven’t fixed it for the new app), but you can leave that out.
Apart from the options mentioned above you can also check out this app which is comprehensive garage door manager which even close the garage door for you after a certain period of time or when someone leaves (and with conditions like motion sensors or hub modes or schedules).
+1 for a simple webcore piston
the push notification definitely will not work. You need to use "send push notification (msg) and store in messages.
You may want to post your piston on the webcore forum and ask for assistance with constructing the piston. You may run into other issues the current structure. There are a few users who enjoy helping others build their pistons.